In general, a policy server manages network resources according to a set of rules, i.e., a policy. While some policy servers simply carve out network resources for undifferentiated data between network routing or switching elements (e.g., from router A to router B), an application-focused policy server manages network resources to fulfill the needs of applications. For example, in a Voice over Internet Protocol (VoIP) application, two network endpoints may wish to establish a VoIP call with one another via the network. The network endpoints request network resources from the policy server for the VoIP call.
FIG. 1 shows one way to implement this VoIP example. A first network endpoint 10 wishes to establish a VoIP call to a second network endpoint 12 via an access network 14. The first endpoint 10 specifies the session attributes in its session setup request to the application server. The application server 18 includes the VoIP application that is responsible for coordinating and setting up the session or call between the endpoints. The application server 18 relays the request for resources associated with the VoIP session to a policy server 20 using PacketCable Multimedia (PCMM) protocol (PKT-TR-MM-ARCH-V01-030627, V01, Jun. 27, 2003; and, PKT-SP-MM-101-030627, Jun. 27, 2003). The application server 18 is synonymous with an application manager 22 that provides the functionality necessary to reserve and manage QoS for the session via the policy server. The policy server in turns controls the network resources to ensure proper treatment is applied to all the media streams associated with the call or session.
Having the functionality of the application manager 22 located in the application server 18 complicates the design of the application server 18. Since some application servers do not need application managers, an application manager constitutes unnecessary cost and complexity for those installations.